ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

2aAO12. Performance limits on acoustic thermometry of ocean climate in the
presence of mesoscale sound-speed variability.

Jeffrey L. Krolik

Sunil Narasimhan

Dept. of Elec. Eng., Duke Univ., Box 90291, Durham, NC 27708

The ability to measure climatic changes in ocean temperature is
fundamentally limited by the presence of mesoscale variability. Because ocean
acoustic propagation depends on the range-averaged sound-speed (and hence
temperature) profile, long-range acoustic transmissions have been proposed as a
means of filtering out mesoscale variability in order to measure a global
warming related trend in mean temperature. The Cramer--Rao lower bound (CRLB)
on the estimation of a change in the mean depth-dependent temperature profile
is presented to determine the highest accuracy which could be achieved by
acoustic thermometry. This work extends [A. B. Baggeroer, J. Acoust. Soc. Am.
95, 2850 (A) (1994)] by evaluating the CRLB for different representations of
the mean depth-dependent temperature profile perturbation with different levels
of a priori knowledge about the mesoscale sound-speed variability. With prior
statistical knowledge of the mesoscale variability, the CRLB indicates that
accurate measurement of the climate signal may be possible using a general
Chebyshev polynomial representation of the mean depth-dependent temperature
perturbation. [Work supported by ONR.]